1. Field of the Invention
The invention relates to a traction drive for a working machine, in particular an industrial truck, including an electrical converter having a generator, which is drive-connected to a combustion engine, and a traction motor, which is combined with the generator in spatial terms to form one structural unit.
2. Technical Considerations
A generic traction drive is disclosed in DE 100 25 089 A1. The electrical machines generally used in the case of such traction drives are air-cooled. At a greater power demand, temperature limits are rapidly reached which could be overcome by means of liquid cooling. However, liquid cooling methods are naturally more complex and often lead to high churning losses in components in which parts rotate in liquid. The degree of efficiency is therefore impaired. In general, an attempt is therefore made to achieve the increased power demand by increasing the rotation speeds of the electrical machines. As regards the electrical machines, this is usually unproblematic, and the degree of efficiency is practically not altered in the process. However, increased power losses result in the downstream components (gear, brakes, etc.).